Secondary Hyperparathyroidism

 Secondary Hyperparathyroidism

In secondary hyperparathyroidism, high levels of PTH occur as a compensation for hypocalcemia rather than as a primary abnormality of the parathyroid glands. This contrasts with primary hyperparathyroidism, which is associated with hypercalcemia.

Secondary hyperparathyroidism can be caused by vitamin D deficiency or chronic renal disease in which the damaged kidneys are unable to produce sufficient amounts of the active form of vitamin D, 1,25-dihydroxycholecalciferol. As discussed in more detail in the next section, the vitamin D deficiency leads to osteo-malacia (inadequate mineralization of the bones), andhigh levels of PTH cause absorption of the bones.

Comments

Post a Comment

Popular posts from this blog

Use of Proteins for Energy

Image
  Use of Proteins for Energy Once the cells are filled to their limits with stored protein, any additional amino acids in the body fluids are degraded and used for energy or are stored mainly as fat or secondarily as glycogen. This degradation occurs almost entirely in the liver, and it begins with deamina-tion,  which is explained in the following section. Deamination.  Deamination means removal of the aminogroups from the amino acids. This occurs mainly by transamination, which means transfer of the amino group to some acceptor substance, which is the reverse of the transamination explained earlier in relation to the synthesis of amino acids. The greatest amount of deamination occurs by the following transamination schema: Note from this schema that the amino group from the amino acid is transferred to a-ketoglutaric acid, which then becomes glutamic acid. The glutamic acid can then transfer the amino group to still other substances or release it in the form of ammonia ...
Read more

Cretinism

  Cretinism Cretinism is caused by extreme hypothyroidism during fetal life, infancy, or childhood. This condition is char-acterized especially by failure of body growth and by mental retardation. It results from congenital lack of a thyroid gland ( congenital cretinism ), from failure of the thyroid gland to produce thyroid hormone because of a genetic defect of the gland, or from iodine lack in the diet ( endemic cretinism ). The severity of endemic cre-tinism varies greatly, depending on the amount of iodine in the diet, and whole populaces of an endemic geo-graphic iodine-deficient soil area have been known to have cretinoid tendencies. A neonate without a thyroid gland may have normal appearance and function because it was supplied with some (but usually not enough) thyroid hormone by the mother while in utero, but a few weeks after birth, the neonate’s movements become sluggish and both physi-cal and mental growth begin to be greatly retarded. Treatment of the neonate with cr...
Read more

Menopause

Image
  Menopause At age 40 to 50 years, the sexual cycle usually becomes irregular, and ovulation often fails to occur.After a few  months to a few years, the cycle ceases altogether, as shown in Figure 81–10.   The period during which the cycle ceases and the female sex hormones diminish to almost none is called  menopause. The cause of menopause is “burning out” of the ovaries. Throughout a woman’s reproductive life, about 400 of the primordial follicles grow into mature follicles and ovulate, and hundreds of thousands of ova degenerate. At about age 45 years, only a few primor-dial follicles remain to be stimulated by FSH and LH, and, as shown in Figure 81–10, the production of estrogens by the ovaries decreases as the number of primordial follicles approaches zero. When estrogen production falls below a critical value, the estrogens can no longer inhibit the production of the gonadotropins FSH and LH. Instead, as shown in Figure 81–9, the gonadotropins FSH and LH (mai...
Read more